Asan Barrage

The Asan river is a river fed by the streams of the western part of the Doon valley. The northern section of the river is known locally as the 'Tons nadi' (a misnomer, the actual Tons nadi is much larger and flows into the Yamuna in the Jaunsar Bawar region at Kalsi); originates from the southern slopes of Mussorie. There are several streams here, that gradually merge into one river that emerges from Robber's cave. The river here is in a U-shaped valley meandering slightly in a south-westerly direction. The river flows through Bijapur canal; a major water pumping site of Dehradun that provides water to houses in the western part of the town through two water canals. It then moves on to Tapkeshwar Mahadev, a popular Shiva shrine before becoming a more shallow, broad valley near Premnagar. The river proceeds south-west, receiving the waters of several streams flowing southward from the northern range spanning Vikas Nagar - Mussorie; and northward from the lower Shiwalik forest hills that separate The Doon valley from Saharanpur district. In the lower section it is known as the 'Asan'. It flows into a relatively flat section which feeds the Asan barrage, the waters of which drain into the Yamuna at Poanta Sahib.

The Asan River has been identified with the Asmanvati of the Rigveda.

The Bird Sanctuary was established in 1967 as a manmade wetland where rivers Yamuna and Asan converged.[6] This area attracts a large number of migratory birds, including birds that are extremely endangered and in the IUCN Red list.[7]

The best time to visit the Barrage is between October and December, and between mid-March to the end of April.[8] The barrage is open all days of the week, from 8am to 6pm.[9] Boating and bird-watching are two activities that tourists enjoy here.